JP5919620B2 - Steel pipe sheet pile mooring berth and its design method - Google Patents

Description

  The present invention relates to a steel pipe sheet pile type mooring berth constructed in a harbor or a river, and more particularly, to a steel pipe sheet pile type mooring berth in which the lower end side of a steel pipe sheet pile wall is embedded in the ground and the upper end side is supported by a tie material with a timber. It is.

Regarding mooring berths constructed in harbors and rivers, there is a sheet pile type revetment structure in which the lower end side of the steel sheet pile is embedded in the ground and the upper end side is supported by a timber with a timber.
Such mooring shores are designed in accordance with “Technical Standards and Explanations for Harbor Facilities” (Japan Port Association).
The sheet pile mooring berth was originally constructed using steel sheet piles (U type, Z type, etc.). However, as the mooring shore becomes deeper, steel sheet piles may not be able to be used as a design. In order to overcome this problem, steel pipe sheet piles with welded joint structures on both sides of steel pipe piles have been used.
Steel pipe sheet pile mooring berths using steel pipe sheet piles are steel pipe sheet piles (JIS A 5530) manufactured at the factory, SKY400 (yield point or yield strength (hereinafter referred to as “steel yield strength”)) is 235 N / mm ² or more ), SKY490 (steel yield strength is constructed using 315N / mm ² or higher).

Kunio Takahashi, Yoshiaki Kikuchi, Yuji Asaki, Analysis of mechanical properties of tie-lot type sheet pile wall, Minato Giken, No.756 1993.6

As for the design method of the sheet pile mooring berth, the depth of sheet pile is determined by the free earth support method, and the virtual beam method is used for stress.
The free earth support method is a method in which the rooting length is determined so that the moments of the main earth pressure and the passive earth pressure are balanced with the tie rod attachment point as the center.
The virtual beam method is a method for determining a sheet pile cross section that can respond to the generated bending stress by applying the main earth pressure from the ground surface to the sea bottom using the tie rod attachment point and the sea bottom as a fulcrum.

These methods have been devised in consideration of the flexibility of the sheet pile, but are not considered in consideration of the difference in rigidity of the sheet pile. Since the steel pipe sheet pile has higher rigidity than the steel sheet pile, there is a problem that the above-described design method cannot be applied as it is.
In order to solve this problem, as shown in Non-Patent Document 1, Takahashi et al., Considering the rigidity of the sheet pile wall, focused on Rowe's method of handling the sheet pile wall as a beam on the elastic floor. This method was compared with the conventional design method (see Non-Patent Document 1).
Since Rowe's method needs to be solved analytically, it is not convenient as a design practice. Therefore, Takahashi et al. Compared Rowe's method with the conventional design method, and calculated the maximum bending moment obtained by the formula ((1)) obtained by the Rowe method or the virtual beam method. Proposed a method of correcting the maximum bending moment that satisfies the Rowe method (Equation (2)).
Equations (1) and (2) are currently used in practice (hereinafter, this method may be referred to as Rowe's correction method). Hereinafter, the equations (1) and (2) will be described.

Flexibility number is an index that is determined by the height H _T of the rigid EI and tie rod attachment point of the sheet pile wall to the sea bottom ^{_{ρ (= H T 4 / EI}} ) is calculated, and multiplied by the ground reaction force coefficient l _h of the Seabed A similarity number ω (= l _h × ρ) which is a combined index is calculated. Here, E is the Young's modulus (MPa) of the steel pipe sheet pile, and I is the cross-sectional second moment (m ⁴ / m) of the steel pipe sheet pile wall per unit width.
Using this ω, the sheet pile penetration length is obtained by equation (1), and the maximum generated moment is obtained by equation (2).
D _F / H _T = 5.0916ω ^-0.2 -0.259 (1)
Here D _F : Necessary penetration length by Rowe method
H _T : Height from the attachment point of Thai material to the bottom of the sea (m)
M _F / M _T = 4.5647ω ^-0.2 +0.1319 (2)
Here, the maximum bending moment that satisfies the M _F : Rowe method
M _T : Maximum bending moment obtained by the virtual beam method

In recent years, the number of M _F / M _T calculated by equation (2) has increased by 1 due to the deepening of the mooring shore due to the increase in size of ships and the increase in design external forces such as earthquakes. When the value exceeds 1 in the equation (2), it is indicated that the maximum bending moment obtained by the conventional method, that is, the virtual beam method is insufficient because the sheet pile wall has high rigidity. In other words, in the case where M _F / M _T exceeds 1, the flexibility of the sheet pile wall is not sufficiently exhibited. The required rigidity of the sheet pile wall is increasing, such as the deepening of the mooring shore due to the increase in size of the ship and the need for better seismic performance than before. As a result, the required penetration length is also increased. This has the problem that the construction cost increases as the steel weight increases.

  An object of this invention is to obtain the steel pipe sheet pile type mooring berth which can suppress steel weight and can suppress construction cost.

In order to solve the above problems, trial calculation of steel pipe sheet pile mooring berths under various conditions was performed. An outline of the trial calculation is shown in FIG.
As shown in FIG. 1, the steel pipe sheet pile mooring berth is formed by rooting the lower end side of the steel pipe sheet pile into the seabed ground and supporting the upper end side with a tie material by a laying work.
The conditions for the trial calculation are as follows.
The water depth is -12m and -15m, the mooring shore top is fixed at + 3m, and the tie attachment point is fixed at + 1.5m. Also, there was no residual water level.
There are three types of submarine ground: loose, medium and hard. The shear resistance angle and ground reaction force coefficient l _h are 30 ° and 24 MN / m ^{3 for} “loose”, 35 ° and 38 MN / m ^{3 for} “medium”, and 40 ° and 58 MN for “hard”. / m ³
A backstone was placed behind the steel pipe sheet pile mooring berth, and the shear resistance angle was 40 °.
Unit volume weight of the ground-water unit volume weight in common to the seabed ground, Urakomi stone 10kN / m ^3, in the in the air was 18kN / m ^3.
Design seismic intensity is designed for level 1 earthquakes, and the design seismic intensity is obtained from the 1D seismic response analysis results of the ground at the examination site using the design seismic motion of each region. In this study, the target seismic intensity is 0.20 and 0.25. It was.
For steel pipe sheet piles, cross section with a pitch of 100 mm from LT500 (L-75 × 75 × 9, T-125 × 9) to φ500t9 to φ1400t16 (φ is diameter (mm), t is plate thickness (mm)) Targeted. As the plate thickness, the minimum plate thickness for each size and the next thicker plate thickness were used.
Characteristic values of the steel yield strength, SKY400 is 235N / mm ^2, SKY490 was 315N / mm ^2. For more high strength material, it was ^{400N / mm 2, 450N / mm} 2, 500N / mm 2, 550N / mm 2, 600N / mm 2, 650N / mm 2, 700N / mm 2, 750N / mm 2 . The cross section was determined so that the value obtained by multiplying the generated stress obtained by the virtual beam method and the modified Rowe method by the structural analysis coefficient γ _a = 1.12.

Figure 2 is a graph for analyzing trial calculation result, the parameter a horizontal axis represents the stiffness of the steel pipe sheet pile wall [rho, the vertical axis to the maximum bending moment that satisfies the method of Rowe determined by M _F and virtual Beam Method maximum bending and the ratio M _F / M _T moment M _T, of the trial calculation result, obtained by plotting the results for ^{235N / mm 2, 315N / mm} 2, 450N / mm 2, 550N / mm 2 in the graph is there.
The broken line shown in FIG. 2 substitutes l _h = 24 MN / m ³ , 38 MN / m ³ , and 58 MN / m ³ for ω in equation (2), respectively, and plots the curves as ρ and M _F / M _T. It is what I subtracted.
As shown in FIG. 2, the SKY400 (yield strength 235N / mm ^2), [rho is from 26 56, M _F / M _T was distributed from 1.04 to 1.40, in SKY490 (yield strength 315N / mm ^2), [rho is It can be seen that 49 to 96 and M _F / M _T are distributed in the range of 1.04 to 1.40. In both cases, M _F / M _T often exceeds 1 and the rigidity of the steel pipe sheet pile wall is high, so that the bending moment generated in the steel pipe sheet pile wall becomes large.
Also, it can be seen that the absolute value of the slope of the curve indicated by the broken line is large, and the bending moment generated greatly changes with a slight change in conditions, and the design is very sensitive.
As long as SKY400 and SKY490, which are steel grades of steel pipe sheet piles currently in general use, are used, M _F / M _T greatly exceeds 1 as described above. As a result, as described above, the penetration depth must be increased. In other words, the construction cost increases as the steel weight increases, and it is not possible to escape from the problem of difficult design.

On the other hand, as shown in FIG. 2, looking at the case where a steel pipe sheet pile yield strength is greater than the characteristic value of the steel yield strength of ^{SKY490 (315N / mm 2) (} 450N / mm 2, 550N / mm 2), in 450 N / mm ^2, [rho is distributed in 0.80~1.11 256, M _F / M _T 94, the 550 N / mm ^2, [rho is 154 from 279, M _F / M _T be distributed from 0.79 to 1.02 I understand.
Therefore, (here, examples of 450 N / mm ² and 550 N / mm ²⁾ characteristic values of the steel yield strength 315N / mm ² greater than steel sheet pile M _F / M _T is largely in comparison with conventional materials by using The steel weight can be reduced and the construction cost can be prevented from increasing. Further, as can be seen from the graph of FIG. 2, the absolute value of the slope of the curve shown by the broken line is small, and it can be seen that a slight change in the condition causes a small change in the bending moment, which is insensitive to the design.
Thus, it was found that it is effective to use a steel pipe sheet pile having a steel yield strength characteristic value larger than at least 315 N / mm ² .

Furthermore, using ρ, it is considered as follows to express the region of ρ in relation to the ground reaction force coefficient l _h .
In FIG. 2, l _h = 24 located on the curve of the MN / m ^3, the value of the rightmost to a ▲ in [rho in FIG when characteristic values of the steel yield strength at a depth of -15m of 315N / mm ² ρ = 82, on the curve of l _h = 58 MN / m ³ , and when the water depth is -15 m and the steel yield strength characteristic value is 315 N / mm ² , 96.
From these [rho as a linear function of l _h (l _h, ρ) is set as a line passing through two points of (24,82) and (58,96). That is, the slope of the straight line is (96-82) / (58-24) = 7/17 = 0.512, and the ρ intercept is 82-7 / 17 × 24 = 72.1176 = 72.118.
Therefore, the use of a steel pipe sheet pile having a steel yield strength characteristic value larger than 315 N / mm ² can be expressed by the following equation (3).
ρ (= H _T ⁴ /EI)>0.412 l _h +72.118 (3) The present invention has been made based on such knowledge, and specifically comprises the following configuration. Is.

(1) A steel pipe sheet pile type mooring berth according to the present invention is a steel pipe sheet pile type mooring berth in which the lower end side is embedded in the ground and the upper end side is supported by a tie material by a tie, and represents the rigidity of the steel pipe sheet pile wall. The parameter ρ (= H _T ⁴ / EI) satisfies the following formula.
ρ (= H _T ⁴ /EI)>0.412 l _h +72.118
However, H _T : Height from the sea floor to the position where the timber is attached (m)
E: Young's modulus of steel sheet pile (MPa)
I: Sectional moment of steel pipe sheet pile wall per unit width (m ⁴ / m)
l _h : Ground reaction force coefficient (MN / m ³ )

(2) Further, in the above (1), the characteristic value of the steel material yield strength that can be used in the design of the steel pipe sheet pile is 400 to 700 N / mm ² .
(3) The steel pipe sheet pile type mooring shore design method according to the present invention is a steel pipe sheet pile type mooring berth design method in which the lower end side is embedded in the ground and the upper end side is supported by a tie material with a tie material,
The parameter ρ (= H _T ⁴ / EI) representing the stiffness of the steel pipe sheet pile wall is set so as to satisfy the following formula.
ρ (= H _T ⁴ /EI)>0.412 l _h +72.118
However, H _T : Height from the sea floor to the position where the timber is attached (m)
E: Young's modulus of steel sheet pile (MPa)
I: Sectional moment of steel pipe sheet pile wall per unit width (m ⁴ / m)
l _h : Ground reaction force coefficient (MN / m ³ )
(4) In the above (3), the steel material yield strength characteristic value that can be used in the design of the steel pipe sheet pile is 400 to 700 N / mm ² .

According to the present invention, a steel pipe sheet pile having a yield strength greater than the SKY490 steel yield strength characteristic value (315 N / mm ² ) is used, so the weight of the steel material used for the steel pipe sheet pile wall can be reduced, and construction Cost can be reduced. In addition, since the load acting on the tie material and the preparatory work is reduced, the weight of both steel materials is reduced.

It is explanatory drawing explaining the conditions of the trial calculation for conceiving the steel pipe sheet pile type mooring shore which concerns on this invention. It is a graph for analyzing a trial calculation result. It is a graph which shows the relationship between the characteristic value of the steel material yield strength of the steel pipe sheet pile type mooring shore of -12m water depth, and the reduction rate of the used steel material weight. It is a graph which shows the relationship between the characteristic value of the steel material yield strength of the steel pipe sheet pile type mooring shore of -15m water depth, and the reduction rate of the used steel material weight.

In the present invention, a steel pipe sheet pile having a yield strength greater than the steel Yield strength characteristic value of SKY490 (315 N / mm ² ) is used, and the value of M _F / M _T is set to about 1.1 at the maximum. By designing rationally in a region where the change in M _F / M _T is small, the weight of steel can be reduced and the construction cost can be reduced.

Below, the range of the characteristic value of suitable steel material yield strength is demonstrated.
When determining the range of the characteristic value of the suitable steel yield strength, the steel pipe sheet pile mooring shore shown in FIG. 1 described above was subjected to trial calculation of the steel pipe sheet pile mooring pier under various conditions in the same manner as described above.
The conditions for the trial calculation are as follows.

The water depth is -12m and -15m, the mooring shore top is fixed at + 3m, and the tie attachment point is fixed at + 1.5m.
There are three types of submarine ground: loose, medium and hard. The shear resistance angle and ground reaction force coefficient l _h are 30 ° and 24 MN / m ^{3 for} “loose”, 35 ° and 38 MN / m ^{3 for} “medium”, and 40 ° and 58 MN for “hard”. / m ³
A backstone was placed behind the steel pipe sheet pile mooring berth, and the shear resistance angle was 40 °.
Unit volume weight of the ground-water unit volume weight in common to the seabed ground, Urakomi stone 10kN / m ^3, in the in the air was 18kN / m ^3.
Design seismic intensity is designed for level 1 earthquakes, and the design seismic intensity is obtained from the 1D seismic response analysis results of the ground at the examination site using the design seismic motion of each region. In this study, the target seismic intensity is 0.20 and 0.25. It was.
For steel pipe sheet piles, cross section with a pitch of 100 mm from LT500 (L-75 × 75 × 9, T-125 × 9) to φ500t9 to φ1400t16 (φ is diameter (mm), t is plate thickness (mm)) Targeted.
Characteristic values of the steel yield strength, SKY400 is 235N / mm ^2, SKY490 was 315N / mm ^2. For more high strength material, it was ^{400N / mm 2, 450N / mm} 2, 500N / mm 2, 550N / mm 2, 600N / mm 2, 650N / mm 2, 700N / mm 2, 750N / mm 2 . The cross section was determined so that the value obtained by multiplying the generated stress obtained by the virtual beam method and the modified Rowe method by the structural analysis coefficient γ _a = 1.12.

The results are shown in Tables 1 and 2. Table 1 shows the case where the water depth is -12 m, and Table 2 shows the case where the water depth is -15 m. In each table, “submarine ground conditions”, “design seismic intensity”, “water depth”, “characteristic value of steel yield strength (N / mm ² )”, “determined steel pipe sheet pile cross section”, “ρ (m ³ / MN ) ”,“ M _F / M _{T ”} ,“ steel pipe sheet pile length (m) ”,“ steel weight (t / m) ”, and“ design value γ _a σ of generated stress ”.

Considering the items shown in the table, for example, in the case of the water depth of -15m shown in Table 2, the ground condition is “medium”, the design seismic intensity is 0.2, the steel pipe sheet pile cross section, M _F / M _T and steel The weights are φ1200t16, 1.15, and 11.47 (t / m) for SKY400 (steel material yield strength characteristic value: 235 N / mm ² ), respectively. Under the same conditions, in SKY490 (steel material yield strength characteristic value: 315 N / mm ² ), the steel pipe sheet pile cross section, M _F / M _T and steel weight are φ1000t14, 1.05 and 9.32 (t / m), respectively.
For these, if the characteristic value of the steel yield strength was 400 N / mm ^2, the steel sheet pile section, M _F / M _T and steel heavy becomes respectively φ800t12,0.938,7.33 (t / m).
Regarding the weight of steel used, SKY400 is 1.0, 0.81 for SKY490, and 0.64 for steel yield strength characteristic value of 400 N / mm ² .
As described above, when the characteristic value of the steel yield strength is 400 N / mm ² , the weight of the steel used can be greatly reduced.

Similar to the above example, in order to investigate the characteristic value of the steel yield strength, the relationship between the characteristic value of the steel yield strength and the reduction rate of the weight of steel used for SKY400 was arranged.
FIG. 3 is a graph showing the results of arrangement. For moored shores at a depth of -12 m, the vertical axis represents the steel weight ratio of the steel material used with respect to SKY400, and the horizontal axis represents the characteristic value of the steel yield strength. In FIG. 4, the vertical axis indicates the reduction rate of the steel material used with respect to SKY400, and the horizontal axis indicates the characteristic value of the steel yield strength for the moored shore at a depth of -15 m.
In the graphs of Figs. 3 and 4, there are 6 cases for each yield strength ("Case1", "Case1M", "Case1D", "Case1-25", "Case1M-25", "Case1D-25" in Tables 1 and 2) ]) And the average value is plotted.

As shown in FIG. 3, it can be seen that at the -12 m water depth, the reduction rate converges at 400 N / mm ² . This is because, even if the steel pipe sheet pile is made smaller in diameter by using the steel yield strength characteristic value that is larger than this, there is no significant difference in the weight of steel used per unit width.
On the other hand, at the -15m water depth, the effect of increasing the characteristic value of the steel yield strength to 700N / mm ² appears. Therefore, from both the result, property values of a suitable steel yield strength seen to be between ^{400N / mm 2 ~700N / mm 2} .

  As described above, according to the present invention, the steel weight can be reliably reduced, and a reasonable range has been clarified. Thereby, the steel material weight used for a steel pipe sheet pile wall can be reduced, and since the load which acts on a tie material and a preparatory work decreases, it leads also to both steel material weight reduction.

1 Steel pipe sheet pile mooring pier 3 Steel pipe sheet pile 5 Ground 7 Thai material 9

Claims (4)

It is a steel pipe sheet pile type mooring berth where the lower end side is embedded in the ground and the upper end side is supported by a tie material with a laying work,
A steel pipe sheet pile mooring berth characterized in that the parameter ρ (= H _T ⁴ / EI) representing the stiffness of the steel pipe sheet pile wall satisfies the following formula.
ρ (= H _T ⁴ /EI)>0.412 l _h +72.118
However, H _T : Height from the sea floor to the position where the timber is attached (m)
E: Young's modulus of steel sheet pile (MPa)
I: Sectional moment of steel pipe sheet pile wall per unit width (m ⁴ / m)
l _h : Ground reaction force coefficient (MN / m ³ ) Steel sheet pile mooring shore according to claim 1, characterized in that the characteristic values of the steel yield strength that can be used in the design of the steel pipe sheet piles and 400~700N / mm ^2. A steel pipe sheet pile type mooring shore design method in which the lower end side is embedded in the ground and the upper end side is supported by a tie material with a tie material,
A design method for a steel pipe sheet pile mooring berth characterized in that a parameter ρ (= H _T ⁴ / EI) representing the stiffness of a steel pipe sheet pile wall satisfies the following formula.
ρ (= H _T ⁴ /EI)>0.412 l _h +72.118
However, H _T : Height from the sea floor to the position where the timber is attached (m)
E: Young's modulus of steel sheet pile (MPa)
I: Sectional moment of steel pipe sheet pile wall per unit width (m ⁴ / m)
l _h : Ground reaction force coefficient (MN / m ³ ) 4. The steel pipe sheet pile type mooring berth design method according to claim 3, wherein a characteristic value of steel yield strength that can be used in the design of the steel pipe sheet pile is 400 to 700 N / mm < ² >.

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